Up to date (2016-08-22), there are 289 problems on LintCode Online Judge.
The number of problems is increasing recently.
Here is the classification of all 289 problems.
For more problems and solutions, you can see my LeetCode repository.
I'll keep updating for full summary and better solutions. Stay tuned for updates.
- Bit Manipulation
- Array
- String
- Linked List
- Math
- Tree
- Stack
- Queue
- Heap
- Hash Tables
- Data Structure
- Sort
- Recursion
- Binary Search
- Breadth-First Search
- Depth-First Search
- Backtracking
- Binary Search Trees
- Dynamic Programming
- Greedy
- OO Design
- System Design
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 1 | A + B Problem | C++ | O(1) | O(1) | Medium | ||
| 82 | Single Number | C++ | O(n) | O(1) | Easy | LeetCode | |
| 83 | Single Number II | C++ | O(n) | O(1) | Easy | LeetCode | |
| 84 | Single Number III | C++ Python | O(n) | O(1) | Medium | CTCI | |
| 142 | O(1) Check Power of 2 | C++ | O(1) | O(1) | Easy | ||
| 179 | Update Bits | C++ | O(1) | O(1) | Medium | CTCI | |
| 181 | Flip Bits | C++ | O(1) | O(1) | Easy | CTCI | |
| 196 | Find the Missing Number | C++ | O(n) | O(1) | Medium | ||
| 365 | Count 1 in Binary | C++ | O(1) | O(1) | Easy | CTCI |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 6 | Merge Sorted Array | Python C++ Java | O(m + n) | O(1) | Easy | LeetCode | Two Pointers |
| 8 | Rotate String | C++ | O(n) | O(1) | Easy | LeetCode | |
| 9 | Fizz Buzz | C++ | O(n) | O(1) | Easy | ||
| 30 | Insert Interval | C++ Python | O(n) | O(1) | Easy | LeetCode, EPI, Google Ladder 18/7 | |
| 31 | Partition Array | C++ | O(n) | O(1) | Medium | Two Pointers | |
| 32 | Minimum Window Substring | C++ | O(n) | O(1) | Medium | LeetCode | |
| 38 | Search a 2D Matrix II | C++ | O(m + n) | O(1) | Medium | EPI | |
| 39 | Recover Rotated Sorted Array | C++ | O(n) | O(1) | Easy | ||
| 46 | Majority Number | C++ | O(n) | O(1) | Easy | LeetCode | |
| 47 | Majority Number II | C++ | O(n) | O(1) | Medium | EPI | |
| 48 | Majority Number III | C++ | O(n) | O(k) | Medium | EPI | |
| 49 | Sort Letters by Case | C++ | O(n) | O(1) | Medium | Two Pointers | |
| 50 | Product of Array Exclude Itself | C++ | O(n) | O(1) | Easy | ||
| 51 | Previous Permutation | C++ | O(n) | O(1) | Medium | ||
| 52 | Next Permutation | C++ | O(n) | O(1) | Medium | LeetCode | |
| 57 | 3 Sum | C++ | O(n^2) | O(1) | Medium | LeetCode | Two Pointers, Sort |
| 58 | 4 Sum | C++ | O(n^3) | O(1) | Medium | LeetCode | Hash |
| 59 | 3 Sum Closest | C++ | O(n^2) | O(1) | Medium | LeetCode | Two Pointers, Sort |
| 64 | Merge Sorted Array II | Python C++ | O(m + n) | O(1) | Easy | LeetCode | Two Pointers |
| 100 | Remove Duplicates from Sorted Array | C++ | O(n) | O(1) | Easy | LeetCode | Two Pointers |
| 101 | Remove Duplicates from Sorted Array II | C++ | O(n) | O(1) | Easy | LeetCode | Two Pointers |
| 133 | Longest Words | C++ | O(n) | O(n) | Easy | ||
| 144 | Interleaving Positive and Negative Numbers | C++ | O(n) | O(1) | Medium | Two Pointers | |
| 161 | Rotate Image | C++ | O(n^2) | O(1) | Medium | LeetCode | |
| 162 | Set Matrix Zeroes | C++ | O(m * n) | O(1) | Medium | LeetCode | |
| 172 | Remove Element | C++ | O(n) | O(1) | Easy | LeetCode | Two Pointers |
| 185 | Matrix Zigzag Traversal | C++ | O(m * n) | O(1) | Easy | ||
| 189 | First Missing Positive | C++ | O(n) | O(1) | Easy | LeetCode, EPI | Hash |
| 190 | Next Permutation II | C++ | O(n) | O(1) | Medium | LeetCode | |
| 200 | Longest Palindromic Substring | C++ | O(n) | O(n) | Medium | LeetCode | Manacher's Algorithm |
| 363 | Trapping Rain Water | C++ | O(n) | O(1) | Medium | LeetCode | Two Pointers, Tricky |
| 373 | Partition Array by Odd and Even | C++ | O(n) | O(1) | Easy | Two Pointers | |
| 374 | Spiral Matrix | C++ | O(m * n) | O(1) | Medium | LeetCode | |
| 381 | Spiral Matrix II | C++ | O(n^2) | O(1) | Medium | LeetCode | |
| 382 | Triangle Count | C++ | O(n^2) | O(1) | Medium | Two Pointers | |
| 383 | Container With Most Water | C++ | O(n) | O(1) | Medium | LeetCode, EPI | Two Pointers |
| 388 | Permutation Sequence | C++ | O(n^2) | O(n) | Medium | LeetCode | |
| 389 | Valid Sudoku | C++ | O(9^2) | O(9) | Easy | Uber,Snapchat,Apple,LeetCode 036 | |
| 402 | Continuous Subarray Sum | Python | O(n) | O(1) | Easy | ||
| 404 | Subarray Sum II | C++ | O(nlogn) | O(n) | Hard | Two Pointers, Binary Search | |
| 405 | Submatrix Sum | C++ | O(m * n^2) | O(m) | Hard | Hash | |
| 406 | Minimum Size Subarray Sum | C++ | O(n) | O(1) | Medium | LeetCode | Two Pointers, Binary Search |
| 539 | Move Zeroes | C++ | O(n) | O(1) | Easy | LeetCode | Two Pointers |
| 601 | Flatten 2D Vector | O(1) | O(1) | Medium | Airbnb,Twitter,Google,LeetCode 251 | ||
| 817 | Range Sum Query 2D - Mutable | Python | O(logMlogN) | O(M*N) | Hard | Google Ladder 18/7 | Bit Indexed Tree, TLE Segment Tree |
| 840 | Range Sum Query - Mutable | Python | O(logn) | O(n) | Medium | Segment Tree | |
| 943 | Range Sum Query - Immutable | Python | O(1) | O(n) | Easy | prefixSum | |
| 1391 | Making A Large Island | O(n^2) | O(n^2) | Hard | Uber,LeetCode 827 | 2D Union Find | |
| 1539 | Flipped The Pixel | Python | O(m*n) | O(1) | Easy | Google Ladder 18/6 | |
| 1555 | Flower Problem | Python | O(n) | O(n) | Hard | Google Ladder 18/6 | Union Find |
| 1628 | Driving Problem | Python | O(n*n) | O(n) | Hard | Google Ladder 18/8 | 2D Union Find |
| 1631 | Interesting Subarray | Python | O(n) | O(n) | Medium | Google Ladder 18/8 | Two Pointers |
| 1641 | Max Remove Order | Python | O(mn) | O(mn) | Hard | Google Ladder 18/9 | Union Find |
| 1643 | Pick Fruits | Python | O(n) | O(n) | Medium | Google Ladder 18/9 | Two Pointers |
| 1644 | Plane Maximum Rectangle | Python | O(n^2) | O(n) | Medium | Google Ladder 18/9 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 13 | strStr | C++ | O(n + k) | O(k) | Easy | LeetCode | KMP Algorithm |
| 53 | Reverse Words in a String | C++ | O(n) | O(1) | Easy | LeetCode, EPI | |
| 54 | String to Integer(atoi) | C++ | O(n) | O(1) | Hard | Uber,LeetCode 8 | |
| 55 | Compare Strings | C++ | O(n) | O(c) | Easy | ||
| 78 | Longest Common Prefix | C++ | O(n) | O(1) | Medium | ||
| 157 | Unique Characters | C++ | O(n) | O(1) | Easy | CTCI | |
| 158 | Two Strings Are Anagrams | C++ | O(n) | O(1) | Easy | ||
| 171 | Anagrams | C++ | O(n * klogk) | O(m) | Easy | LeetCode, EPI | |
| 212 | Space Replacement | C++ | O(n) | O(1) | Easy | ||
| 407 | Plus One | C++ | O(n) | O(1) | Easy | LeetCode | |
| 408 | Add Binary | C++ | O(n) | O(1) | Easy | LeetCode | |
| 415 | Valid Palindrome | C++ | O(n) | O(1) | Easy | Uber, LeetCode 125 | |
| 417 | Valid Number | C++ | O(n) | O(1) | Hard | LeetCode | Automata |
| 420 | Count and Say | C++ | O(n * 2^n) | O(2^n) | Easy | LeetCode | |
| 422 | Length of Last Word | C++ | O(n) | O(1) | Easy | LeetCode | |
| 524 | Left Pad | C++ | O(p + n) | O(1) | Easy | LeetCode | |
| 633 | Find the Duplicate Number | Python | O(n) | O(1) | Hard | Google Ladder 18/7 | fast-slow-pointers |
| 640 | One Edit Distance | Medium | Uber, LeetCode 161 | ||||
| 927 | Reverse Words in a String ii | Medium | Uber, LeetCode 186 |
|1086|Repeated String Match|Python| O(n*(m+n)) | O(m+n) | Easy | Google Ladder 18/6, LeetCode | | |1540|Can Convert|Python| O(min(s, t)) | O(1) | Easy | Google Ladder 18/6 | Two Pointers | |1542|Nexttime Norepeat|Python| O(1)) | O(1) | Easy | Google Ladder 18/6 | | |1545|Last Closest Time|Python| O(1)) | O(1) | Easy | Google Ladder 18/6 | | |1554|Lasttime Norepeat|Python| O(1)) | O(1) | Easy | Google Ladder 18/6 | | |1580|Transition String|Python| O(n)) | O(n) | Medium | Google Ladder 18/7 | | |1625|Words Compression|Python| O(n+k)) | O(k) | Hard | Google Ladder 18/8 | KMP Algorithm | |1627|Word Segmentation|Python| O(n)) | O(1) | Easy | Google Ladder 18/8 | | |1632|Count Email Groups|Python| O(n)) | O(n) | Easy | Google Ladder 18/8 | | |1634|Secret Word|Python| O((n-w)*w)) | O(w) | Easy | Google Ladder 18/9 | | |1642|Query String|Python| O(n)) | O(1) | Hard | Google Ladder 18/9 | Suffix Tree? |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 16 | Merge Two Sorted Lists | C++ | O(n) | O(1) | Easy | LeetCode, EPI | |
| 35 | Reverse Linked List | C++ | O(n) | O(1) | Easy | Uber,LeetCode 206, EPI | |
| 36 | Reverse Linked List II | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 96 | Partition List | C++ | O(n) | O(1) | Easy | LeetCode | |
| 98 | Sort List | C++ | O(nlogn) | O(logn) | Medium | LeetCode, EPI | |
| 99 | Reorder List | C++ | O(n) | O(1) | Medium | LeetCode | |
| 102 | Linked List Cycle | C++ | O(n) | O(1) | Medium | LeetCode | |
| 103 | Linked List Cycle II | C++ | O(n) | O(1) | Hard | LeetCode | |
| 104 | Merge k Sorted Lists | C++ | O(n * logk) | O(1) | Medium | LeetCode | Heap, Divide and Conquer |
| 105 | Copy List with Random Pointer | C++ | O(n) | O(1) | Medium | LeetCode | |
| 106 | Convert Sorted List to Binary Search Tree | C++ | O(n) | O(logn) | Medium | LeetCode, EPI | |
| 112 | Remove Duplicates from Sorted List | C++ | O(n) | O(1) | Easy | LeetCode, EPI | |
| 113 | Remove Duplicates from Sorted List II | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 166 | Nth to Last Node in List | C++ | O(n) | O(1) | Easy | LeetCode | |
| 167 | Two Lists Sum | C++ | O(n) | O(1) | Easy | LeetCode | |
| 170 | Rotate List | C++ | O(n) | O(1) | Medium | LeetCode | |
| 173 | Insertion Sort List | C++ | O(n^2) | O(1) | Easy | LeetCode | |
| 174 | Remove Nth Node From End of List | C++ | O(n) | O(1) | Easy | LeetCode | |
| 223 | Palindrome Linked List | C++ | O(n) | O(1) | Medium | LeetCode | |
| 372 | Delete Node in the Middle of Singly Linked List | C++ | O(1) | O(1) | Easy | CTCI | |
| 380 | Intersection of Two Linked Lists | C++ | O(m + n) | O(1) | Easy | LeetCode | |
| 450 | Reverse Nodes in k-Group | C++ | O(n) | O(1) | Hard | LeetCode | |
| 451 | Swap Nodes in Pairs | C++ Python | O(n) | O(1) | Medium | Uber,Microsoft,Bloomberg,LeetCode 024 | |
| 452 | Remove Linked List Elements | C++ | O(n) | O(1) | Naive | LeetCode | |
| 511 | Swap Two Nodes in Linked List | C++ | O(n) | O(1) | Medium |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 7 | Binary Tree Serialization | C++ | O(n) | O(h) | Medium | Uber,LeetCode 297 | |
| 85 | Insert Node in a Binary Search Tree | C++ | O(h) | O(1) | Easy | ||
| 88 | Lowest Common Ancestor | C++ | O(n) | O(h) | Medium | EPI | |
| 175 | Invert Binary Tree | C++ | O(n) | O(h) | Easy | LeetCode | |
| 442 | Implement Trie | C++ | O(n) | O(1) | Medium | LeetCode | Trie |
| 1577 | Sum of Leaf Nodes | Python | O(n) | O(1) | Hard | Google Ladder 18/7 | Morris |
| 1624 | Max Distance | Python | O(n*l) | O(n*l) | Hard | Google Ladder 18/8 | Trie |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 12 | Min Stack | C++ | O(n) | O(1) | Medium | Uber,LeetCode 155, EPI | |
| 40 | Implement Queue by Two Stacks | C++ | O(1), amortized | O(n) | Medium | EPI | |
| 66 | Binary Tree Preorder Traversal | C++ | O(n) | O(1) | Easy | LeetCode, EPI | Morris Traversal |
| 67 | Binary Tree Inorder Traversal | C++ | O(n) | O(1) | Easy | LeetCode, EPI | Morris Traversal |
| 68 | Binary Tree Postorder Traversal | C++ | O(n) | O(1) | Easy | LeetCode, EPI | Morris Traversal |
| 122 | Largest Rectangle in Histogram | C++ | O(n) | O(n) | Hard | LeetCode, EPI | Ascending Stack |
| 126 | Max Tree | C++ | O(n) | O(n) | Hard | Descending Stack | |
| 367 | Expression Tree Build | C++ | O(n) | O(n) | Hard | ||
| 368 | Expression Evaluation | C++ | O(n) | O(n) | Hard | ||
| 369 | Convert Expression to Polish Notation | C++ | O(n) | O(n) | Hard | ||
| 370 | Convert Expression to Reverse Polish Notation | C++ | O(n) | O(n) | Hard | ||
| 421 | Simplify Path | C++ | O(n) | O(n) | Medium | LeetCode | |
| 423 | Valid Parentheses | C++ Python | O(n) | O(n) | Easy | Uber,Airbnb,Google,Facebook,Amazon,Twitter,LeetCode 020 | |
| 424 | Evaluate Reverse Polish Notation | C++ | O(n) | O(n) | Medium | LeetCode | |
| 473 | Add and Search Word | C++ | O(min(n, h)) | O(min(n, h) | Medium | LeetCode | Trie |
| 510 | Maximal Rectangle | C++ | O(m * n) | O(n) | Hard | LeetCode | Ascending Stack |
| 528 | Flatten Nested List Iterator | C++ | O(n) | O(h) | Medium | LeetCode | |
| 1001 | Asteroid Collision | O(n) | O(n) | Medium | Uber, LeetCode 735 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 362 | Sliding Window Maximum | C++ | O(n) | O(k) | Hard | EPI | Deque, Tricky |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 4 | Ugly Number II | C++ | O(n) | O(1) | Medium | CTCI | BST, Heap |
| 81 | Data Stream Median | C++ | O(nlogn) | O(n) | Hard | EPI | BST, Heap |
| 130 | Heapify | C++ | O(n) | O(1) | Medium | ||
| 364 | Trapping Rain Water II | C++ | O(m * n * (logm + logn)) | O(m * n) | Hard | BFS, Heap, Tricky | |
| 471 | Top K Frequent Words | Medium | Uber, LeetCode 692 | Heap, Bucket Sort | |||
| 518 | Super Ugly Number | C++ | O(n * k) | O(n + k) | Medium | LeetCode | BST, Heap |
| 1571 | Top K GPA | Python | O(n * logk) | O(k) | Medium | Google Ladder 18/7 | Heap |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 56 | 2 Sum | C++ | O(n) | O(n) | Medium | Uber,LeetCode 001 | |
| 124 | Longest Consecutive Sequence | C++ | O(n) | O(n) | Medium | LeetCode, EPI | |
| 128 | Hash Function | C++ | O(n) | O(1) | Easy | ||
| 129 | Rehashing | C++ | O(n) | O(n) | Medium | ||
| 138 | Subarray Sum | C++ | O(n) | O(n) | Easy | ||
| 186 | Max Points on a Line | C++ | O(n^2) | O(n) | Medium | LeetCode | |
| 211 | String Permutation | C++ | O(n) | O(1) | Easy | ||
| 384 | Longest Substring Without Repeating Characters | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 386 | Longest Substring with At Most K Distinct Characters | C++ | O(n) | O(n) | Medium | ||
| 432 | Find the Weak Connected Component in the Directed Graph | C++ | O(nlogn) | O(n) | Medium | Union Find | |
| 434 | Number of Islands II | C++ | O(k) | O(k) | Hard | Union Find | |
| 488 | Happy Number | C++ Python | O(k) | O(k) | Easy | Uber, Airbnb, Twitter,LeetCode 202 | |
| 547 | Intersection of Two Arrays | C++ | O(m + n) | O(min(m, n)) | Easy | EPI, LeetCode | Two Pointers, Binary Search |
| 548 | Intersection of Two Arrays II | C++ | O(m + n) | O(min(m, n)) | Easy | EPI, LeetCode | Two Pointers, Binary Search |
| 828 | Word Pattern | Python | O(n) | O(c), c is number of unique patterns | Easy | Uber, Dropbox Leetcode 290 | |
| 829 | Word Pattern II | O(n * C(n-1, c-1)) | O(n+c) | Hard | Uber, Dropbox Leetcode 291,10,44 | ||
| 1443 | longest-ab-substring | Python | O(n) | O(n) | Medium | prefixSum, Hash Table |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 134 | LRU Cache | C++ | O(1) | O(k) | Hard | LeetCode, EPI | List, Hash |
| 1245 | All O`one Data Structure | O(1) | O(k) | Hard | Uber, LeetCode 432 | Double Linked List, Hash |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 2 | Trailing Zeros | C++ | O(1) | O(1) | Easy | LeetCode | |
| 3 | Digit Counts | C++ | O(1) | O(1) | Medium | CTCI | |
| 114 | Unique Paths | C++ | O(min(m, n)) | O(1) | Easy | LeetCode, CTCI | DP, Math |
| 147 | Narcissistic Number | Python | O(10^n*n) | Easy | CAT | Brute Force | |
| 163 | Unique Binary Search Trees | C++ | O(n) | O(1) | Medium | CTCI | DP, Math, Catalan Number |
| 180 | Binary Represention | C++ | O(1) | O(1) | Hard | CTCI | |
| 197 | Permutation Index | C++ | O(n^2) | O(1) | Easy | ||
| 198 | Permutation Index II | C++ | O(n^2) | O(n) | Medium | ||
| 394 | Coins in a Line | C++ | O(1) | O(1) | Easy | ||
| 411 | Gray Code | C++ | O(2^n) | O(1) | Medium | LeetCode | |
| 413 | Reverse Integer | C++ | O(1) | O(1) | Medium | LeetCode | |
| 414 | Divide Two Integer | C++ | O(1) | O(1) | Medium | LeetCode | |
| 418 | Integer to Roman | C++ | O(n) | O(1) | Medium | LeetCode | |
| 419 | Roman to Integer | C++ | O(n) | O(1) | Medium | LeetCode | |
| 428 | Pow(x, n) | C++ | O(1) | O(1) | Medium | LeetCode | |
| 445 | Cosine Similarity | C++ Python | O(n) | O(1) | Easy | ||
| 517 | Ugly Number | C++ | O(1) | O(1) | Easy | CTCI, LeetCode | |
| 1544 | Magic Square | Python | O(n*n) | O(n*n) | Hard | Google Ladder 18/6 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 5 | Kth Largest Element | C++ | O(n) ~ O(n^2) | O(1) | Medium | EPI | Two Pointers, Quick Sort |
| 80 | Median | C++ | O(n) | O(1) | Easy | EPI | |
| 139 | Subarray Sum Closest | C++ | O(nlogn) | O(n) | Medium | Sort | |
| 143 | Sort Colors II | C++ | O(n) | O(1) | Medium | ||
| 148 | Sort Colors | C++ | O(n) | O(1) | Medium | LeetCode | |
| 156 | Merge Intervals | C++ | O(nlogn) | O(1) | Easy | LeetCode, EPI | |
| 184 | Largest Number | C++ | O(nlogn) | O(1) | Medium | LeetCode | |
| 366 | Fibonacci | C++ | O(n) | O(1) | Easy | ||
| 379 | Reorder array to construct the minimum number | C++ | O(nlogn) | O(1) | Medium | LeetCode | |
| 387 | The Smallest Difference | C++ | O(max(m, n) * log(min(m, n))) | O(1) | Medium | Two Pointers, Binary Search | |
| 399 | Nuts & Bolts Problem | C++ | O(nlogn) | O(logn) | Medium | Quick Sort | |
| 400 | Maximum Gap | C++ Python | O(n) | O(n) | Hard | LeetCode | Bucket Sort |
| 463 | Sort Integers | C++ | O(n^2) | O(1) | Easy | Insertion Sort, Selection Sort, Bubble Sort | |
| 464 | Sort Integers II | C++ | O(nlogn) | O(n) | Easy | Merge Sort, Heap Sort, Quick Sort | |
| 507 | Wiggle Sort II | C++ | O(n) on average | O(1) | Medium | LeetCode | Tri Partition |
| 508 | Wiggle Sort | C++ | O(n) | O(1) | Medium | LeetCode | |
| 1465 | Order Of Tasks | Python | O(n) | O(1) | Medium | Greedy |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 22 | Flatten List | C++ | O(n) | O(h) | Easy | ||
| 72 | Construct Binary Tree from Inorder and Postorder Traversal | C++ | O(n) | O(n) | Medium | LeetCode, EPI | |
| 73 | Construct Binary Tree from Preorder and Inorder Traversal | C++ | O(n) | O(n) | Medium | LeetCode, EPI | |
| 93 | Balanced Binary Tree | C++ Python | O(n) | O(h) | Easy | LeetCode | Tree DP |
| 94 | Binary Tree Maximum Path Sum | C++ Python | O(n) | O(h) | Medium | LeetCode | Tree DP |
| 95 | Validate Binary Search Tree | C++ | O(n) | O(h) | Medium | LeetCode | |
| 97 | Maximum Depth of Binary Tree | C++ | O(n) | O(h) | Easy | Uber,LinkedIn,LeetCode 104 | |
| 131 | Building Outline | C++ Python | O(nlogn) | O(n) | Hard | EPI | Sort, BST |
| 140 | Fast Power | C++ | O(logn) | O(1) | Medium | ||
| 155 | Minimum Depth of Binary Tree | C++ | O(n) | O(h) | Easy | LeetCode | |
| 164 | Unique Binary Search Trees II | C++ | O(n * 4^n / n^(3/2)) | O(n) | Medium | LeetCode | |
| 177 | Convert Sorted Array to Binary Search Tree With Minimal Height | C++ | O(n) | O(logn) | Easy | LeetCode | |
| 201 | Segment Tree Build | C++ | O(n) | O(h) | Medium | Segment Tree, BST | |
| 202 | Segment Tree Query | C++ | O(h) | O(h) | Medium | Segment Tree, BST | |
| 203 | Segment Tree Modify | C++ | O(h) | O(h) | Medium | Segment Tree, BST | |
| 205 | Interval Minimum Number | C++ | build tree: O(n), query: (h) | O(h) | Hard | Segment Tree, BST | |
| 206 | Interval Sum | C++ | build tree: O(n), query: O(logn) | O(n) | Hard | Segment Tree, BIT | |
| 207 | Interval Sum II | C++ | build tree: O(n), query: O(logn), modify: O(logn) | O(n) | Hard | Segment Tree, BIT | |
| 245 | Subtree | C++ | O(m * n) | O(1) | Easy | Morris Traversal |
|
| 247 | Segment Tree Query II | C++ | O(h) | O(h) | Hard | Segment Tree, BST | |
| 248 | Count of Smaller Number | C++ | build tree: O(n), query: O(logn) | O(h) | Medium | Segment Tree, BST | |
| 371 | Print Numbers by Recursion | C++ | O(n) | O(n) | Medium | ||
| 375 | Clone Binary Tree | C++ | O(n) | O(h) | Easy | ||
| 378 | Convert Binary Search Tree to Doubly Linked List | C++ | O(n) | O(h) | Medium | ||
| 439 | Segment Tree Build II | C++ | O(n) | O(h) | Medium | Segment Tree, BST | |
| 453 | Flatten Binary Tree to Linked List | C++ | O(n) | O(h) | Easy | LeetCode | |
| 469 | Identical Binary Tree | C++ | O(n) | O(h) | Easy | ||
| 532 | Reverse Pairs | C++ | O(nlogn) | O(n) | Medium | variant of Count of Smaller Number before itself | BIT, Merge Sort |
| 535 | House Robber III | C++ | O(n) | O(h) | Medium | LeetCode | |
| XXX | Topological Sort | Python | O(V+E) | O(h) | Medium | Topological Sort |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 14 | First Position of Target | C++ | O(logn) | O(1) | Easy | ||
| 28 | Search a 2D Matrix | C++ | O(logm + logn) | O(1) | Easy | LeetCode | |
| 60 | Search Insert Position | C++ | O(logn) | O(1) | Easy | LeetCode | |
| 61 | Search for a Range | C++ | O(logn) | O(1) | Medium | LeetCode | |
| 62 | Search in Rotated Sorted Array | C++ | O(logn) | O(1) | Medium | LeetCode | |
| 63 | Search in Rotated Sorted Array II | C++ | O(logn) | O(1) | Medium | LeetCode | |
| 65 | Median of two Sorted Arrays | C++ | O(log(min(m, n))) | O(1) | Hard | Uber,LeetCode 4, EPI | Tricky |
| 74 | First Bad Version | C++ | O(logn) | O(1) | Medium | ||
| 75 | Find Peak Element | C++ Python | O(logn) | O(1) | Medium | LeetCode | |
| 76 | Longest Increasing Subsequence | C++ Python | O(nlogn) | O(n) | Medium | CTCI, Leetcode 300 | |
| 141 | Sqrt(x) | C++ | O(logn) | O(1) | Easy | LeetCode | |
| 159 | Find Minimum in Rotated Sorted Array | C++ | O(logn) | O(1) | Medium | LeetCode | |
| 160 | Find Minimum in Rotated Sorted Array II | C++ | O(logn) | O(1) | Medium | LeetCode | |
| 183 | Wood Cut | C++ | O(nlogL) | O(1) | Medium | ||
| 390 | Find Peak Element II | C++ Java Python | O(m + n) | O(1) | Hard | ||
| 437 | Copy Books | C++ | O(nlogp) | O(1) | Hard | UVa 714 | |
| 458 | Last Position of Target | Python | O(logn) | O(1) | Easy | Google Ladder 18/7 | |
| 1077 | Falling Squares | O(nlogn) | O(n) | Hard | Uber, LeetCode 699 | Segment Tree | |
| 1564 | Interval Search | Python | O(logn) | O(1) | Easy | Google Ladder 18/7 | |
| 1623 | Minimal Distance in the Array | Python | O(min(MlogN, NlogN)) | O(1) | Google Ladder 18/8 | ||
| 1626 | Salary Adjustment | Python | O(log(target/n)) | O(1) | Easy | Google Ladder 18/8 | |
| 1633 | Strings that Satisfies the Condition | Python | O(n*len(s)) | O(1) | Easy | Google Ladder 18/9 | |
| 1629 | Find the Nearest Store | Python | O(min(HlogS, SlogS)) | O(1) | Easy | Google Ladder 18/8 | |
| 1645 | Least Subsequences | Python | O(nlogn) | O(n) | Medium | Google Ladder 18/9 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 69 | Binary Tree Level Order Traversal | C++ | O(n) | O(n) | Medium | Uber, LeetCode 102 | BFS |
| 70 | Binary Tree Level Order Traversal II | C++ | O(n) | O(n) | Medium | LeetCode | BFS |
| 71 | Binary Tree Zigzag Level Order Traversal | C++ | O(n) | O(n) | Medium | LeetCode | BFS |
| 120 | Word Ladder | C++ | O(n * d) | O(d) | Medium | LeetCode | BFS |
| 121 | Word Ladder II | C++ | O(n * d) | O(d) | Hard | LeetCode | BFS, Back Trace |
| 127 | Topological Sorting | C++ | O(|V|+|E|) | O(|E|) | Medium | DFS, BFS | |
| 137 | Clone Graph | C++ | O(|V|+|E|) | O(|V|) | Medium | BFS | |
| 176 | Route Between Two Nodes in Graph | C++ | O(n) | O(n) | Medium | DFS, BFS | |
| 178 | Graph Valid Tree | C++ | O(|V| + |E|) | O(|V| + |E|) | Medium | LeetCode | |
| 431 | Find the Connected Component in the Undirected Graph | C++ | O(n) | O(n) | Medium | BFS | |
| 477 | Surrounded Regions | C++ | O(m * n) | O(m + n) | Medium | LeetCode | |
| 630 | Knight Shortest Path II | Python | O(m * n) | O(m * n) | Easy | BFS or DP | |
| 825 | Bus Station | Python | O(#of stops) | O(#of stops) | Hard | Google Ladder 18/6 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 90 | K Sum II | C++ | O(k * C(n, k)) | O(k) | Medium | ||
| 376 | Binary Tree Path Sum | C++ | O(n) | O(h) | Easy | LeetCode | |
| 433 | Number of Islands | C++ | O(m * n) | O(m * n) | Easy | LeetCode | DFS |
| 480 | Binary Tree Paths | C++ | O(n * h) | O(h) | Easy | LeetCode | |
| 795 | 4-Way Unique Pathsp | Python | O(m*n) | O(m*n) | Medium | ||
| 1630 | Interesting String | Python | O(n) | Medium | Google Ladder 18/8 | ||
| 1646 | CheckWords | Python | O(n) | Easy | Google Ladder 18/9 | DFS + Memorization |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 15 | Permutations | C++ | O(n * n!) | O(n) | Medium | LeetCode, EPI | |
| 16 | Permutations II | C++ | O(n * n!) | O(n) | Medium | LeetCode, EPI | |
| 17 | Subsets | C++ | O(n * 2^n) | O(1) | Medium | Uber,LeetCode 78 | |
| 18 | Subsets II | C++ | O(n * 2^n) | O(1) | Medium | LeetCode | |
| 33 | N-Queens | C++ | O(n * n!) | O(n) | Medium | LeetCode, EPI | |
| 34 | N-Queens II | C++ | O(n * n!) | O(n) | Medium | LeetCode, EPI | |
| 123 | Word Search | C++ | O(m * n * l) | O(l) | Medium | LeetCode | |
| 132 | Word Search II | C++ | O(m * n * l) | O(l) | Hard | Trie, DFS | |
| 135 | Combination Sum | C++ | O(k * n^k) | O(k) | Medium | LeetCode | DFS |
| 136 | Palindrome Partitioning | C++ | O(2^n) | O(n) | Easy | LeetCode, EPI | |
| 152 | Combinations | C++ | O(k * n^k) | O(k) | Medium | LeetCode, EPI | |
| 153 | Combination Sum II | C++ | O(k * C(n, k)) | O(k) | Medium | LeetCode | DFS |
| 425 | Letter Combinations of a Phone Number | C++ | O(n * 4^n) | O(n) | Medium | LeetCode | |
| 426 | Restore IP Addresses | C++ | O(1) | O(1) | Medium | LeetCode | |
| 427 | Generate Parentheses | C++ | O(4^n / n^(1/2)) | O(n) | Medium | Uber,LeetCode 022 | |
| 802 | Sudoku Solver | O((9!)^9) | O(1) | Hard | Uber, LeetCode 37 | ||
| 1576 | Optimal Match | Python | ?? | O(n) | Hard | Google Ladder 18/9 | Hungary Algorithm |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 11 | Search Range in Binary Search Tree | C++ | O(n) | O(h) | Medium | EPI | |
| 86 | Binary Search Tree Iterator | C++ | O(1) | O(h) | Hard | LeetCode | |
| 87 | Remove Node in Binary Search Tree | C++ | O(h) | O(h) | Hard | ||
| 249 | Count of Smaller Number before itself | C++ | O(nlogn) | O(n) | Hard | BST, BIT, Divide and Conquer, Merge Sort | |
| 360 | Sliding Window Median | C++ | O(nlogw) | O(w) | Hard | BST, Tricky | |
| 391 | Number of Airplanes in the Sky | C++ | O(nlogn) | O(n) | Easy | BST, Heap | |
| 401 | Kth Smallest Number in Sorted Matrix | C++ | O(klog(min(m, n, k))) | O(min(m, n, k)) | Medium | BST, Heap | |
| 902 | Kth Smallest Element in a BST | Python | O(k) | O(k) | Easy | Google Ladder 18/7,Uber LeetCode 230 | BST |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 20 | Dices Sum | C++ | O(n^2) | O(n) | Hard | ||
| 29 | Interleaving String | Python C++ | O(m * n) | O(min(m, n)) | Medium | LeetCode 97, EPI | |
| 43 | Maximum Subarray III | C++ | O(k * n) | O(k * n) | Hard | ||
| 77 | Longest Common Subsequence | C++ | O(m * n) | O(min(m, n)) | Medium | ||
| 79 | Longest Common Substring | C++ | O(m * n) | O(min(m, n)) | Medium | ||
| 89 | K Sum | C++ | O(k * n * t) | O(n * t) | Hard | ||
| 91 | Minimum Adjustment Cost | C++ | O(k * n * t) | O(k) | Medium | ||
| 92 | Backpack | C++ Python | O(m * n) | O(m) | Easy | ||
| 107 | Word Break | C++ | O(n * l^2) | O(n) | Medium | LeetCode, EPI | |
| 108 | Palindrome Partitioning II | C++ | O(n^2) | O(n) | Medium | LeetCode, EPI | |
| 109 | Triangle | C++ Python | O(n) | O(n) | Easy | LeetCode, EPI | |
| 110 | Minimum Path Sum | C++ | O(m * n) | O(min(m, n)) | Easy | LeetCode, EPI | |
| 111 | Climbing Stairs | C++ | O(n) | O(1) | Easy | LeetCode | |
| 115 | Unique Paths II | C++ | O(m * n) | O(min(m, n)) | Easy | LeetCode, CTCI | DP, Math |
| 118 | Distinct Subsequences | C++ | O(m * n) | O(m) | Medium | LeetCode | DP |
| 119 | Edit Distance | C++ | O(m * n) | O(min(m, n)) | Medium | LeetCode, CTCI | DP |
| 125 | Backpack II | C++ | O(m * n) | O(m) | Medium | ||
| 149 | Best Time to Buy and Sell Stock | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 150 | Best Time to Buy and Sell Stock II | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 151 | Best Time to Buy and Sell Stock III | C++ | O(n) | O(1) | Medium | LeetCode, EPI | |
| 154 | Regular Expression Matching | C++ | O(m * n) | O(m) | Hard | Uber,Airbnb,LeetCode 10 | DP, Recursion |
| 168 | Burst Balloons | C++ | O(n^3) | O(n^2) | Medium | LeetCode | |
| 191 | Maximum Product Subarray | C++ | O(n) | O(1) | Medium | LeetCode | |
| 392 | House Robber | C++ | O(n) | O(1) | Medium | LeetCode | |
| 393 | Best Time to Buy and Sell Stock IV | C++ | O(k * n) | O(k) | Hard | LeetCode, EPI | |
| 395 | Coins in a Line II | C++ | O(n) | O(1) | Medium | ||
| 396 | Coins in a Line III | C++ | O(n^2) | O(n) | Hard | ||
| 397 | Longest Increasing Continuous subsequence | C++ | O(n) | O(1) | Easy | ||
| 398 | Longest Increasing Continuous subsequence II | C++ | O(m * n) | O(m * n) | Hard | ||
| 403 | Continuous Subarray Sum II | C++ | O(n) | O(1) | Medium | EPI | |
| 430 | Scramble String | C++ | O(n^4) | O(n^3) | Hard | LeetCode | |
| 435 | Post Office Problem | C++ | O(k * n^2) | O(n) | Hard | PKU 1160 | |
| 436 | Maximal Square | C++ | O(m * n) | O(n) | Medium | LeetCode | |
| 512 | Decode Ways | C++ | O(n) | O(1) | Medium | LeetCode | |
| 513 | Perfect Squares | C++ | O(n * sqrt(n)) | O(n) | Medium | LeetCode | |
| 514 | Paint Fence | C++ | O(n) | O(1) | Easy | LeetCode | |
| 515 | Paint House | C++ | O(n) | O(1) | Medium | LeetCode | |
| 516 | Paint House II | C++ | O(n * k) | O(k) | Hard | LeetCode | |
| 534 | House Robber II | C++ | O(n) | O(1) | Medium | LeetCode | |
| 564 | Backpack VI | C++ | O(n * t) | O(t) | Medium | ||
| 630 | Knight Shortest Path II | Python | O(m * n) | O(m * n) | Easy | ||
| 631 | Maximal Square II | Python | O(m * n) | O(n) | Easy | Amazon | |
| 741 | Calculate Maximum Value II | Python | O(n^2) | O(n^2) | Easy | Interval DP | |
| 843 | Digital Flip | Python | O(n) | O(1) | Medium | Microsoft | |
| 953 | The Biggest Score On The Tree | Python | O(n) | O(h) | Medium | Airbnb | Tree DP |
| 1224 | Count The Repetitions | Python | O(n1 * len(s1)) | O(n1) | Super Hard | ||
| 1383 | Subtree Count | Python | O(n) | O(n) | Medium | ||
| 1384 | Segment Stones Merge | Python C++ Java | O(n^3) | O(n^3) | Super Hard | 3d DP | |
| 1395 | The Barycentre Of The Trees | Python | O(n) | O(n) | Hard | Tree DP | |
| 1400 | Fermat Point Of Graphs | Python | O(n) | O(n) | Super Hard | Tree DP | |
| 1414 | Eat The Beans | Python C++ | O(w*r) | O(w*r) | Medium | ||
| 1444 | Dyeing Problem | Python | O(n) | O(1) | Medium | Alibaba | |
| 1447 | Calculation the Sum of Path | Python C++ Java | O(l * w) | O(l * w) | Medium | ||
| 1448 | Card Game | Python C++ Java | O(n * totalProfit * totalCost) | O(totalProfit * totalCost) | Medium | ||
| 1470 | The Game Of Take Numbers | Python | O(n*n) | O(n) | Medium | Google Ladder 18/7 | Interval |
| 1538 | Card Game II | Python | O(n * totalMoney) | O(totalMoney) | Easy | Google Ladder 18/6 | backpack |
| 1541 | Put Box | Python | O(m*n) | O(m*n) | Medium | Google Ladder 18/6 | Interval |
| 1543 | Unique Path IV | Python | O(h*w) | O(h) | Medium | Google Ladder 18/6 | Coordinate |
| 1621 | Cut Connection | Python | O(m*n) | O(1) | Medium | Google Ladder 18/8 | Coordinate |
| 1640 | Duplicate Digits | Python | O(1) | Hard | Google Ladder 18/9 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 41 | Maximum Subarray | C++ | O(n) | O(1) | Easy | LeetCode | |
| 42 | Maximum Subarray II | C++ | O(n) | O(n) | Medium | ||
| 44 | Minimum Subarray | C++ | O(n) | O(1) | Easy | ||
| 45 | Maximum Subarray Difference | C++ | O(n) | O(n) | Medium | ||
| 116 | Jump Game | C++ | O(n) | O(1) | Medium | LeetCode | |
| 117 | Jump Game II | C++ | O(n) | O(1) | Medium | LeetCode | |
| 182 | Delete Digits | C++ | O(n) | O(n) | Medium | ||
| 187 | Gas Station | C++ | O(n) | O(1) | Easy | LeetCode | |
| 192 | Wildcard Matching | C++ | O(m + n) | O(1) | Hard | LeetCode | Greedy, DP, Recursion |
| 402 | Continuous Subarray Sum | C++ | O(n) | O(1) | Medium | EPI | |
| 412 | Candy | C++ | O(n) | O(n) | Hard | LeetCode | Greedy |
| 552 | Create Maximum Number | C++ | O(k * (m + n + k)) ~ O(k * (m + n + k^2)) | O(m + n + k^2) | Hard | LeetCode | Greedy, DP |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 204 | Singleton | C++ Python | O(1) | O(1) | Easy | ||
| 208 | Assignment Operator Overloading (C++ Only) | C++ | O(n) | O(1) | Medium | ||
| 496 | Toy Factory | C++ Python | O(1) | O(1) | Easy | ||
| 497 | Shape Factory | C++ Python | O(1) | O(1) | Easy | ||
| 498 | Parking Lot | C++ Python Java | O(n * m * k) | O(n * m * k) | Hard | CTCI | OO Design |
| 708 | Elevator System OO Design | Python C++ Java | Hard | OO Design | |||
| 709 | Restaurant OO Design | C++ Java | Hard | OO Design | |||
| 710 | Hotel OO Design | C++ Java | Hard | OO Design | |||
| 712 | Vending Machine OO Design | C++ Java | Medium | OO Design | |||
| 714 | Black Jack OO Design | C++ Java | Medium | OO Design | |||
| 731 | Restaurant II OO Design | C++ Java | Hard | OO Design | |||
| 732 | Hotel II OO Design | C++ Java | Hard | OO Design | |||
| 746 | Tic Tac Toe OO Design | C++ Java Python | Hard | OO Design | |||
| 747 | Coffee Maker OO Design | C++ Java | Medium | OO Design, decorator | |||
| 748 | Kindle OO Design | C++ Java | Easy | OO Design, factory |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| Sys1 | News Feed System | ||||||
| 501 | Mini Twitter | C++ Python | O(klogu) | O(t + f) | Medium | Heap | |
| 560 | Friendship Service | Python | Easy | Hash | |||
| Sys2 | Database and Cache | ||||||
| 519 | Consistent Hashing | Python | O(nlogn) | O(n) | Easy | Heap | |
| 520 | Consistent Hashing II | Python | Medium | bisect, random | |||
| 538 | Memcache | Python | Easy | Hash | |||
| 502 | mini-cassandra | Python | Easy | Hash | |||
| 134 | LRU Cache | Python | O(1) | O(k) | Hard | Uber,LeetCode 146 | OrderedDict, Doubly LinkedList + Hash |
| 24 | LFU Cache | Python | O(1) | O(k) | Hard | Doubly LinkedList + Hash | |
| Sys3 | Tiny URL | ||||||
| 232 | Tiny Url | Python | Easy | Hash, Dict | |||
| 522 | Tiny Url II | Python | Medium | Hash, Dict | |||
| 526 | Load Balancer | Python | Easy | Set, random | |||
| Sys4 | Location Based Service | ||||||
| 529 | Geohash | Python | Medium | Geohash | |||
| 530 | Geohash II | Python | Medium | Geohash | |||
| 525 | Mini Uber | Python | Medium | ||||
| 509 | Mini Yelp | Python | Hard | Geohash, Bisect | |||
| Sys5 | Web Crawler and Google Suggestion | ||||||
| 500 | Inverted Index | Python | Easy | ||||
| 523 | Url Parser | Python | Hard | Regex | |||
| 442 | Implement Trie (Prefix Tree) | Python | Medium | Trie | |||
| 559 | Trie Service | Python | Medium | Trie | |||
| 527 | Trie Serializatioin | Python | Hard | Trie, Stack | |||
| 231 | Typeahead | Python | Medium | Set | |||
| 234 | Webpage Crawler | Python | Hard | Thread | |||
| Sys6 | Distributed File System | ||||||
| 566 | GFS Client | Python | Easy | ||||
| 565 | Heart Beat | Python | Easy | ||||
| Sys7 | Map Reduce | ||||||
| 499 | Word Count (Map Reduce) | Python | Easy | ||||
| 549 | Top K Frequent Words (Map Reduce) | C++ | Medium | ||||
| 503 | Anagram (Map Reduce) | Python | Easy | ||||
| 504 | Inverted Index (Map Reduce) | Python | Easy | ||||
| 654 | Sparse Matrix Multiplication | Python | Easy | ||||
| Sys8 | Bigtable | ||||||
| 556 | Standard Bloom Filter | Python | Medium | Hash | |||
| 555 | Counting Bloom Filter | Python | Medium | Hash | |||
| 486 | Merge K Sorted Arrays | Python | Easy | Heap | |||
| Sys9 | Message System, Rate Limiter and Design Pattern | ||||||
| 505 | Web logger | Python | Easy | ||||
| 215 | Rate Limiter | Python | Hard | Bisect |